Electromagnetic radiation and its types-Jayam chemistry learners

Types of electromagnetic radiation

The electromagnetic spectrum is a continuum arrangement of electromagnetic radiations in the increasing order of their wavelengths or decreasing order of their frequencies. The Scottish physicist James Clerk Maxwell discovered electromagnetism of light during his watershed treatment in 1864. It disclosed the combined interrelation between the electric and magnetic fields in the propagating light wave. This blog article discusses types of electromagnetic radiation along with the electromagnetic theory of light.

Postulates of electromagnetic wave theory:

The light was a wave for folks early in the nineteenth century, but the nature of light transmission was unrevealed till 1864. Maxwell proposed electromagnetic wave theory to describe the electric and magnetic field couple characteristics in the disseminating light beam. 

It explained the wave nature of light and emphasized the continuous transmission of radiant energy. The key postulates of this electromagnetic wave theory are:

1. Light is a traveling wave of electric and magnetic fields. Hence, it is electromagnetic while transmitting.

2. Maxwell postulated that the accelerating electric field of radiation is the source of electromagnetism. A continuously varying electric field generates a magnetic field, and changes in the induced magnetic field create an electric field. Thus, when an electrically charged particle moves under acceleration, the resulting alternating electric and magnetic fields propagate as an electromagnetic wave, known as light. Consequently, light exhibits all wave characteristics, such as wavelength, frequency, and amplitude.

3. Both these oscillating electric and magnetic fields are at a right angle to one another. Also, perpendicular to the direction of propagation of light.

4. Electromagnetic radiant waves can travel through matter mediums such as solid, liquid, and gas in addition to space. Consequently, the medium is not a requisite for light propagation.

5. Light does not displace the medium particles through which it propagates. Instead, the variation in comparative strengths of electric and magnetic fields duo showcase its transmission.

6. Various electromagnetic radiations have different wavelengths and frequencies though they travel with the same velocity of 3 x 10¹⁰ cm/sec in space. Therefore, the speed of light in a vacuum is constant.

7. The energy that transmits continuously between bodies as rays or radiations is called radiant energy. Examples of radiant energy are visible light, heat, gamma rays, infrared rays, microwaves, X-rays, and so on.

Advantages of electromagnetic wave theory:

1. The unification of electricity, magnetism, and light provided a deeper understanding of electromagnetic radiations, leading to applications in physics, engineering, astronomy, and telecommunications.
2. Maxwell’s equations enabled the quantitative analysis and prediction of electromagnetic phenomena, resulting in technologies like antennas, radars, and electronics. 
3. The electromagnetic wave theory also predicted unknown forms of radiation, such as radio waves and microwaves, which were later discovered and applied in various fields. This predictive power allowed for the exploration and utilization of new regions of the electromagnetic spectrum.

Disadvantages of electromagnetic wave theory:

The major disadvantages of electromagnetic wave theory are:

• It could not explain the photoelectric effect and the Compton effect.
• Additionally, it failed to accurately account for the occurrence of line spectra by the atoms of chemical elements.

Questions and answers on electromagnetic wave theory:

1. Why are the oscillating electric and magnetic fields of electromagnetic radiation perpendicular to each other and to the direction of light propagation?

Answer: 

Electromagnetic waves propagate as transverse waves, meaning the oscillations of the electric and magnetic fields occur perpendicular to the direction of wave propagation. This is a requirement for the wave to satisfy Maxwell's equations, which describe the fundamental relationship between electric and magnetic fields. 

The electric and magnetic fields of an electromagnetic wave are mutually perpendicular to each other. This is a consequence of the fact that a time-varying electric field generates a magnetic field, and a time-varying magnetic field generates an electric field, as described by Maxwell's equations. The electric and magnetic fields are thus coupled and must be perpendicular to each other in order to propagate as a self-sustaining electromagnetic wave.

2. Why doesn't electromagnetic radiation need a medium for propagation?

Answer: 

Electromagnetic radiation can travel through a vacuum because the electric and magnetic fields that constitute the radiation are self-sustaining. These fields regenerate each other through electromagnetic induction, as described by Maxwell's equations, allowing the wave to propagate without requiring a physical medium.

3. Why can electromagnetic radiation travel through a vacuum?

Answer: 

Electromagnetic radiation, such as visible light, radio waves, and X-rays, can propagate through a vacuum without the need for a physical medium. This is because the propagation of electromagnetic radiation does not rely on the presence of a material medium, unlike the propagation of mechanical waves, such as sound waves, which require a medium like air or water.

 In a vacuum, where there are no particles or material present, the electric and magnetic fields can still oscillate and propagate, as they are not dependent on the presence of a medium to sustain the wave.

4. Why can't electromagnetic radiation displace the medium particles through which it propagates?

Answer: 

Electromagnetic radiation, such as light, X-rays, or radio waves, cannot displace the particles of the medium through which it propagates due to several key factors:

Nature of Transverse Waves:

Electromagnetic radiation consists of transverse waves, where the oscillations of electric and magnetic fields are perpendicular to the direction of wave propagation. This transverse nature means the radiation does not exert a direct force that could displace the particles of the medium.

Insufficient Momentum:

Unlike mechanical waves like sound, electromagnetic waves do not have significant momentum to impart on the particles of the medium. The momentum of an electromagnetic wave is typically much smaller than that of the particles in the medium, making it ineffective at pushing or displacing them.

Interaction with Medium:

When electromagnetic radiation interacts with a medium, the particles in the medium can absorb or scatter the radiation, but they are not displaced by the wave. The energy of the radiation is absorbed, causing particles to vibrate or heat up, or it is scattered in different directions, but the particles themselves are not physically displaced.

Wavelength and Particle Size Mismatch:

The wavelength of most electromagnetic radiation is much larger than the size of individual particles in a medium, such as air or water molecules. This mismatch in scale means the radiation cannot effectively "push" or displace the particles, as they are much smaller than the wavelength of the radiation.

In summary, the transverse nature of electromagnetic waves, their lack of significant momentum, and the mismatch between the wavelength of the radiation and the size of medium particles all contribute to the inability of electromagnetic radiation to directly displace the particles through which it propagates.

5.What is the speed of light, and how is it calculated?

Answer:  

Maxwell's wave equation demonstrated that the speed of light, denoted as c, is determined by a combination of constants from the laws of electrostatics and magnetostatics.

c = ¹ ⁄ _{(ε⁰μ⁰)^1⁄2}

Where, ε⁰ is the permittivity of free space and its value is equal to 8.85 X 10^-12 square coloumb per newton per meter

μ⁰ is the magnetic permeability of free space and it's value is 1.26 X 10^-6 newton square seconds per square coloumb

c = ¹ ⁄ _{(8.85 X 10^-12 X 1.26 X 10^-6)^1⁄2}

c = 3 X 10⁸ metres per second = 3 X 10¹⁰ cm per second

6. What is the reason for the constant speed of light in a vacuum?

Answer: 

The constant speed of light in a vacuum is attributed to the fundamental properties of electromagnetic waves and the nature of space itself. According to Maxwell's equations, which describe the behavior of electromagnetic fields, the speed of light in a vacuum is determined by the electric permittivity and magnetic permeability of free space. 

These constants dictate the maximum speed at which electromagnetic waves, including light, can propagate through empty space.

Electromagnetic radiation and its properties:

The form of radiant energy associated with the oscillations of electric and magnetic fields of an accelerated charged particle is known as electromagnetic radiation. As a form of energy, electromagnetic radiation can exhibit both particle and wave characteristics.

James Clerk Maxwell explained that electromagnetic energy is transmitted continuously from one body to another in the form of electromagnetic waves. Thus, electromagnetic radiation is a propagating light wave consisting of paired electric and magnetic fields. Different wavelengths of the electromagnetic spectrum are produced depending on the frequency of oscillation.

Electromagnetic radiation is associated with waves that can propagate themselves ("radiate") without the ongoing influence of the moving charges that generated them. This demonstrates the self-sustaining nature of electromagnetic radiation, enabling it to travel through a vacuum at a constant speed of 3 X10⁸ m/s. 

Additionally, the energy associated with electromagnetic radiation is directly proportional to its intensity. Therefore, radiation of any frequency can have varying amounts of energy depending on its intensity. However, this assumption about radiant energy failed to explain the phenomenon of blackbody radiation.

Before this, in 1704, Sir Isaac Newton proposed the corpuscular theory of light, which suggested that light is a form of radiant energy composed of streams of particles called corpuscles. This theory successfully explained phenomena such as reflection and refraction, proving the particle nature of light. However, it failed to account for wave properties like interference and diffraction. Consequently, the corpuscular theory of light was rejected, and it was proposed that the transmission of radiant energy occurs in the form of transverse waves.

The particle nature of light energy was further confirmed by Max Planck in 1900 with the Quantum Theory of Radiation. According to this theory, electromagnetic radiation is absorbed or emitted by a body discontinuously in the form of small packets called photons. Thus, electromagnetic radiation consists of a flow of discrete energy packets. The energy of a photon depends on the frequency of the electromagnetic radiation, and the two are related by the equation E = nhν

Consequently, electromagnetic radiation carrying photons with a fixed energy will have a definite frequency, meaning the energy of light rays is quantized. The frequency of an electromagnetic wave is determined by the energy of the photons it carries, as these two factors have a directly proportional relationship, E ∝ ν

Based on this understanding, the electromagnetic spectrum was divided into different regions according to the frequency of the electromagnetic radiations. The intensity of electromagnetic radiation depends on the number of photons present in it. This quantum perspective of electromagnetic radiation explained phenomena such as black body radiation and the photoelectric effect. Ultimately, these experimental findings led Einstein to propose that light possesses both particle and wave characteristics, demonstrating its dual nature.

As both the particle and wave character of light gave a valid argument for the existence of electromagnetic radiations of varying frequencies or wavelengths. Hence, the electromagnetic spectrum is divided into seven regions based on radiant energy variations. The seven kinds of electromagnetic radiations are;

1. Gamma rays
2. X-rays
3. Ultraviolet rays
4. Visible radiations
5. Infrared radiations
6. Microwaves
7. Radio waves

Occurrence of electromagnetic radiations:

The Sun's surface emits various electromagnetic radiations into space. Different wavelengths of light typically originate from different regions of the Sun’s atmosphere or from specific atoms radiating at particular wavelengths (spectral emission lines). For instance, visible light comes from the photosphere (or surface), while most infrared light comes from the lower chromosphere just above it. Many high-energy UV and X-ray photons are emitted from the Sun’s outer atmosphere, known as the corona.

Similarly, stars, galaxies, and other celestial bodies also emit these radiations. The seven types of electromagnetic radiation are gamma rays, X-rays, ultraviolet rays, visible light, infrared radiation, microwaves, and radio waves.

Additionally, non-renewable fossil fuels such as coal, petroleum, oil, and natural gas are stored forms of energy received from the Sun as electromagnetic radiation millions of years ago. The only energy source not originating from the Sun is that from nuclear reactors.

Properties of electromagnetic radiation:

1. These are transverse waves.
2. They do not deflect by electric and magnetic fields.
3. They are neutral and do not carry any charge.
4. When electromagnetic radiation passes through two different mediums, its path deviates from the original. It depicts a change in its wavelength, whereas its frequency remains constant.
5. Speed of electromagnetic radiation changes with the nature of the propagating medium. It is because light velocity is low in denser mediums such as solids.

Question and answers on electromagnetic radiation:

1. What is the principle of electromagnetic radiation?

Answer:

The principle of electromagnetic radiation is based on the behavior of electric and magnetic fields. According to electromagnetic theory, when an electric charge accelerates, it generates oscillating electric and magnetic fields that propagate outward from the source in the form of waves. These waves are collectively known as electromagnetic radiation and can travel through a vacuum at the speed of light.

Key principles of electromagnetic radiation are;

Oscillating Fields: 

Electromagnetic radiation consists of oscillating electric and magnetic fields that are perpendicular to each other and to the direction of wave propagation.

Wave-Particle Duality: 

Electromagnetic radiation exhibits both wave-like properties (such as interference and diffraction) and particle-like properties (such as the photoelectric effect), where the radiation can be considered as quantized packets of energy called photons.

Propagation through Vacuum: 

Unlike mechanical waves, electromagnetic waves do not require a medium to travel and can propagate through a vacuum.

Spectrum: 

Electromagnetic radiation covers a broad spectrum of wavelengths and frequencies, from gamma rays with very short wavelengths to radio waves with very long wavelengths.

Energy and Frequency Relationship: 

The energy of the radiation is directly proportional to its frequency and inversely proportional to its wavelength, described by the equation, E =hν

Where,

E = Energy of electromagnetic radiation

h = Planck's constant

ν =Frequency of electromagnetic radiation

These principles underpin the wide range of applications for electromagnetic radiation, from radio communications to medical imaging and understanding the universe.

2. Why is electromagnetic radiation used?

Answer:

Electromagnetic radiation is used for a variety of purposes due to its versatile properties and broad spectrum of wavelengths. Here are some key reasons why it is utilized:

Communication: 

Radio waves, microwaves, and infrared radiation are widely used in communication technologies, including radio broadcasting, television, mobile phones, and internet data transmission.

Medical Applications:

X-rays and gamma rays are crucial in medical imaging and treatments, such as X-ray radiography, CT scans, and cancer radiation therapy.

Scientific Research:

Ultraviolet, visible, and infrared light are used in various spectroscopic techniques to study the properties of substances and for astronomical observations to explore the universe.

Everyday Technology:

Visible light is essential for human vision, and infrared radiation is used in remote controls, thermal imaging, and night-vision equipment.

Energy:

Solar panels convert sunlight (a form of electromagnetic radiation) into electrical energy, providing a renewable energy source.

Navigation and Radar:

Electromagnetic waves are used in radar systems for navigation, weather forecasting, and military applications.

Heating and Cooking: 

Microwaves are used in microwave ovens for cooking food, and infrared radiation is used in heaters.

The diverse applications of electromagnetic radiation stem from its ability to carry energy across different wavelengths, making it indispensable in modern technology and scientific exploration.

Electromagnetic range

The table below provides a summary of the wavelength and frequency ranges of electromagnetic waves. To gain a clearer understanding of the range of radiation wavelengths, the following conversion information may be useful.

• 1m = 100cm 
• 1nm = 10^-9m 
• 1A⁰ = 10^-10m 
• 1μm = 10^-6m
• 1mm = 10^-3 m

Table-1: A concise table detailing the frequency and wavelength ranges of different types of electromagnetic radiation.
Type of electromagnetic radiation	Frequency range expressed in Hz	Wavelength range expressed in meter(m)	Wavelength range expressed in centimeter(cm)	Wavelength range expressed in nanometer(nm)	Wavelength range expressed in Angstrom(A0)
Gamma rays	From 1020 to 1024	Less than 10-12	Less than 10-10	Less than 10-3	Less than 10-2
X-rays	From 1017 to 1020	From 10-9 to 10-12	From 10 -7 to 10-10	From 1 to 10-3	From 10 to 10-2
Ultraviolet(UV) rays	From 1015 to 1017	From 4 x 10-7 to 10-9	From 4 x 10-5 to 10-7	From 400 to 1	From 4000 to 10
Visible radiations	From 4 to 7.5 x 1014	From 75 x 10-8 to 4 x 10-7	From 75 x 10-6 to 4 x 10-5	From 750 to 400	From 7500 to 4000
Infrared radiations	From 1013 to 1014	From 25 x 10-6 to 2.5 x 10-6	From 25 x 10-4 to 2.5 x 10-4	From 25000 to 2500	From 250000 to 25000
Microwaves	3 x 1011 to 1013	From 10-3 to 25 x 10-6	From 10-1 to 25 x 10-4	From 106 to 25000	From 107 to 250000
Radiowaves	Less than 3 x 1011	Greater than 10-3	Greater than 10-1	Greater than 106	Greater than 107

Electromagnetic waves:

What is electromagnetic wave?

An electromagnetic wave is a quantized harmonic oscillation of paired electric and magnetic fields produced by an accelerated electrically charged particle.

The frequency of an electromagnetic wave matches the frequency of the accelerated charged particles that generate it. Thus, the electromagnetic spectrum is a classification of seven types of electromagnetic waves based on their radiant energy in descending order, known as the electromagnetic wave spectrum.

The wavelengths of EM waves in this spectrum range approximately from 10^-16 meters to 10⁸ meters.

All about electromagnetic waves:

The energy transmission by electromagnetic wave is continuous:

An electromagnetic wave consists of packets of radiant energy that move continuously from one point to another. This continuous flow of photons, adhering to the laws of classical quantum mechanics, initially failed to explain the particle nature of electromagnetic rays experimentally.

Transverse nature of EM waves:

The electromagnetic waves are transverse, meaning the time-varying electric and magnetic fields oscillate perpendicular to the direction of wave propagation. Consequently, electromagnetic waves do not require a medium for their propagation and can travel through empty space at a constant speed, known as the speed of light.

Electromagnetic wave is sinusoidal:

Electromagnetic waves propagate as sine waves, following a trigonometric sine function waveform. These waves carry radiant energy and momentum, exerting force on other charged particles they encounter, which causes their acceleration and changes their direction of velocity, but not their magnitude.

Waves of light ray are independent:

Despite originating from accelerated charged particles, electromagnetic waves do not rely on their source for propagation. They are self-sustaining and can travel long distances from their source. Consequently, electromagnetic energy from the Sun and other celestial bodies reaches the Earth's surface, serving as sources of heat and light essential for life on Earth.

EM emissions and atomic spectrum:

The amount of heat energy that electromagnetic radiation spreads depends on the type of electromagnetic ray. Simply put, a tungsten bulb produces more heat than a CFL because it radiates mostly in the infrared region.

Similarly, warm objects in our daily life emit varying levels of energy. For instance, iron glows red when heated to 460 degrees Celsius because it emits energy in the visible region, which the human eye can see.

This demonstrates that every chemical element can absorb and emit electromagnetic energy at specific frequencies unique to each element. The intensity of light absorbed or emitted by different chemical elements varies, aiding in their identification during compound analysis.

Question and answers on electromagnetic waves:

1. Why is an electromagnetic wave considered light?

Answer:

An electromagnetic wave is considered light because light is a specific range of electromagnetic waves that are visible to the human eye. The term "light" often refers to the entire electromagnetic spectrum, including visible light, ultraviolet light, infrared light, X-rays, gamma rays, microwaves, and radio waves.

These waves are all forms of electromagnetic radiation, which are generated by oscillating electric and magnetic fields. The visible portion of this spectrum is what we commonly refer to as light, but in a broader sense, all electromagnetic waves share the same fundamental properties, allowing them to be categorized under the umbrella of "light."

Question and answers on characteristics of EM wave:

1. How to calculate wavelength?

Answer:

We can determine the wavelength of light using either of the following two methods:

(a) If the energy of a photon is given, we can use the relation:

E = ^hc⁄_λ

This indicates an inverse relationship between electromagnetic energy and wavelength.

(b) If the frequency of light is given, we can use the formula:

c = λν

λ = ^c⁄_ν

This also denotes an inverse relationship between frequency and wavelength.

Depending on the data provided, either of these formulas can be used to calculate the wavelength of light.

2. What is the SI unit of wavelength?

Answer:

The SI unit of radiation wavelength is meter and the symbol 'm' denotes it.

3. What is wave speed?

Answer:

Wave speed is the distance a wave travels in a given amount of time. Alternatively, it can be defined as the number of meters a wave travels in one second.

Therefore, wave speed is the ratio of the distance traveled by the wave to the time taken, expressed in seconds.

Wave speed = ^{Distance travelled expressed in meter} ⁄ _{Time taken expressed in seconds}

4. How to calculate λ and ν of EM radiation?

Answer:

The product of the frequency and wavelength of electromagnetic radiation is a constant known as the speed of light, which indicates their inversely proportional relationship.

c = λν

λν = constant = 3 x 10⁸ m/s.

As a result, light with a higher frequency will have a shorter wavelength, such as gamma rays, while light with a lower frequency will have a longer wavelength, like radio waves.

5. What electromagnetic spectrum wavelengths are visible to humans?

Answer:

Visible radiations, ranging from 400 nm to 700 nm, are perceptible to humans. The sequence of these wavelengths in increasing order forms the electromagnetic light spectrum. Additionally, the wavelength of visible light determines its color.

Table-2: Table illustrating wavelengths and corresponding colors of visible light radiation
Color of visible light radiation	Radiation wavelength expressed in nm
Violet	From 380 to 450
Indigo	From 420 to 440
Blue	From 450 to 495
Green	From 495 to 570
Yellow	From 570 to 590
Orange	From 590 to 620
Red	From 620 to 750

Notably, arranging these colors by their first letters spells out VIBGYOR, representing the seven colors of sunlight. Therefore, the visible light spectrum within the electromagnetic spectrum is also referred to as the solar spectrum or VIBGYOR spectrum.

6. Which colour make white light?

Answer:

White light is a combination of seven different radiations having wavelengths in the range 400-700 nm.

7. Which colour has the longest wavelength?

Answer:

The color red has the longest wavelength, ranging from 620 to 750 nm, and it marks the end of the visible spectrum.

8. Which colour has the highest speed?

Answer:

Red light, with its longer wavelength, can travel faster than other colors because it can cover longer distances in one second. This illustrates the direct relationship between the velocity of light and its wavelength, where velocity is proportional to wavelength (ν ∝ λ).

9. Which colour has the most energy?

Answer:

Violet has the highest energy among the colors in the visible spectrum of EMS. This energy variation can be explained by the wavelength of its radiation. With a wavelength ranging from 380 to 450 nm, violet possesses the highest energy. Specifically, the energy of violet color is 46.382 x 10^-20 joules

10. What is the highest frequency of human?

Answer:

The maximum frequency detectable by humans is 7 x 10¹⁴ Hz. Additionally, the frequency range tolerated by humans varies from 10⁹ to 10¹⁴ Hz. These frequencies are classified as non-ionizing radiations, which pose minimal risk to biological systems because they carry relatively low energy that is insufficient to damage living cells.

11. What frequency is infrared?

Answer:

The frequency of infrared radiation lies between 10¹³ to 10¹⁴.

12. How many hertz is green?

Answer:

To find frequency of green color, we can use this relation, ν = ^c⁄_λ

Where, c = velocity of light and its value is 3 x 10⁸ m/s

λ = wavelength of green color which is 495 nm = 495 x 10^-9 m

After substituting these values in the above equation, we get 6 x 10¹⁴ Hz.

Similarly, if λ value is 570 nm, we get 5.26 x 10¹⁴ Hz.

Hence, the frequency of green color varies from 5.26 x 10¹⁴ Hz to 6 x 10¹⁴ Hz.

13. Which color is more visible?

Answer:

Red color is highly visible due to its longer wavelength, allowing it to travel faster. Therefore, red is prominently used in critical contexts such as warning signs and traffic signals to ensure visibility over longer distances and effectively alert people.

Electromagnetic energy:

Electromagnetic energy is the amount of energy associated with the oscillations of electric and magnetic field pairs in electromagnetic radiation. This energy is released when an external force accelerates an electric charge, generating a wave of alternating magnetic and electric fields that detaches from the charge and moves independently through the medium.

Electromagnetic energy, also known as a photon, is an uncharged, massless particle. Consequently, nothing can travel faster than light, as it consists of photons. Interestingly, despite the theoretically infinite energy of a light ray, it cannot physically displace the particles of matter it interacts with.

Electromagnetic energy is a combination of heat and light that can be transmitted from one body to another. This energy is quantized, leading to seven distinct regions in the electromagnetic spectrum based on its variation.

The order of electromagnetic waves, from highest to lowest energy, is: Gamma rays > X-rays > UV > Visible > IR > Microwave > Radio waves, indicating that gamma rays have the highest energy.

If the energy of an electromagnetic ray lies between 26.1727 x 10^-19 Joules to 52.3454 x 10^-19 Joules, it is visible to the human eye and is referred to as visible light. The rest of the electromagnetic spectrum, which is not visible, is called the invisible light spectrum. Electromagnetic energy of light radiation can be expressed in terms of its wavelength and frequency.

The higher the frequency of an electromagnetic ray, the greater its energy. The impact on biological or living systems depends on the radiation's frequency. Radiations with frequencies above 10¹⁶ Hz, including UV rays, X-rays, and γ-rays, are termed ionizing radiations. These radiations are energetic enough to break covalent bonds and can cause biological damage. Conversely, radiations with frequencies between 10⁹ Hz to 10¹⁴ Hz are non-ionizing and are useful for cooking.

Electromagnetic spectrum:

Define electromagentic spectrum?

Electromagnetic spectrum is a pattern of unboundedly diffused light in the increasing or decreasing manner of their wavelengths and frequencies.

Even though it is a continuous spectrum of electromagnetic radiation having frequencies below 1 Hz to above 10²⁵ Hz with no outermost edge, it has only seven named regions. They are gamma rays, X-rays, ultraviolet rays, visible & infrared rays, microwaves, and radio waves. Their names symbolize their origin, effect on biological systems, and interaction with matter.

The electromagnetic radiations having frequencies from 10⁹ to 10¹⁴ Hz are non-ionizing. Similarly, electromagnetic waves having more than 10¹⁶ Hz frequency are ionizing.

The study of the electromagnetic spectrum is significant in spectroscopy and astronomy. It is helpful to identify new chemical substances or unknown celestial matters.

How electromagentic spectrum is produced?

No single object on Earth emits the entire electromagnetic spectrum, which spans a vast range of wavelengths and frequencies from radio waves to gamma rays. However, certain sources can emit a predominant portion or specific region of the spectrum based on the energy of the electromagnetic waves.

The Sun, for instance, emits solar radiation that includes visible light, ultraviolet light, infrared, radio waves, X-rays, and gamma rays. Every object radiates energy as heat and light unless it is at absolute zero, where molecular motion ceases. Warm objects, in particular, emit infrared radiation as part of the electromagnetic spectrum.

All objects absorb and emit radiation. When absorption equals emission, an object's temperature remains constant. Energy absorption excites electrons to higher energy levels, while energy emission occurs when high-energy electrons fall to lower levels, releasing light or electromagnetic radiation. This spectrum of emitted electromagnetic radiations, known as the atomic spectrum, varies with different wavelengths for different elements.

The Sun emits a continuous spectrum from its hot surface and discrete frequencies specific to its atomic composition.

The familiar examples of discrete-frequency electromagnetic spectrum include the distinct colors of fluorescent gas lamps, dyes, sodium lamps' yellow, mercury lamps' blue-green, and various laser colors.

Artificial sources like X-ray machines, lasers, and microwave ovens can generate specific portions of the spectrum, but not the entire range.

Certain natural processes like black body radiation from hot objects can produce a range of wavelengths, but still not the complete spectrum.

Even the most powerful human-made sources, like particle accelerators or nuclear reactors, are only able to generate specific bands of the electromagnetic spectrum, not the full spectrum.

Applications of electromagnetic spectrum:

The electromagnetic spectrum has a wide range of applications across various fields.

Communication:

Radio waves are used for radio and television broadcasting, as well as for wireless communication technologies like WiFi, Bluetooth, and cellular networks.

Microwaves are utilized in radar systems and satellite communications.

Imaging and Sensing:

Visible light is used in photography and videography.

Infrared radiation is used in night vision, thermal imaging, and remote sensing.

X-rays and gamma rays are used in medical imaging for diagnostic purposes, as well as in security scanning.

Energy Generation and Transmission:

Visible light and infrared radiation are used in solar energy generation.

Microwaves are used in microwave ovens for heating and cooking.

Scientific Research:

Different regions of the spectrum are used in various scientific applications, such as spectroscopy, astronomy, and particle physics.

Ultraviolet radiation is used in sterilization and disinfection processes.

Medical Applications:

X-rays and gamma rays are used in cancer treatment and diagnostic procedures.

Ultraviolet light is used in the treatment of certain skin conditions.

Industrial Applications:

Infrared radiation is used in heat treatment and drying processes in manufacturing.

Ultraviolet light is used for curing and drying of various materials, as well as in water purification.

The wide range of wavelengths and frequencies within the electromagnetic spectrum allows for a diverse set of applications that are essential in modern technology, science, and daily life.

Question and answers on electromagnetic spectrum:

1. Are the solar spectrum and the electromagnetic spectrum the same thing?

Answer:

No, the solar spectrum and the electromagnetic spectrum are not the same thing.

The solar spectrum refers specifically to the range of electromagnetic radiation emitted by the Sun. It includes wavelengths from ultraviolet to infrared, with the peak emission in the visible light range.

The electromagnetic spectrum, on the other hand, is a much broader classification that encompasses all forms of electromagnetic radiation, including not just the solar spectrum, but also wavelengths beyond what the Sun emits, such as radio waves, microwaves, X-rays, and gamma rays.

So while the solar spectrum is a part of the larger electromagnetic spectrum, the two terms are not interchangeable. The electromagnetic spectrum describes the full range of all electromagnetic radiation, of which the solar spectrum is just one component.

2. Why is the electromagnetic spectrum continuous?

Answer:

The electromagnetic spectrum is continuous due to the nature of the underlying physical phenomena that produce electromagnetic radiation.

The key reasons why the electromagnetic spectrum is continuous are:

Unified electromagnetic theory:

The electromagnetic spectrum is a unified representation of various types of electromagnetic radiation, which are all manifestations of the same fundamental electromagnetic field.

This field is described by Maxwell's equations, which provide a comprehensive mathematical framework that encompasses the entire spectrum.

Continuous range of frequencies and wavelengths:

Electromagnetic radiation can be produced across a continuous range of frequencies and their corresponding wavelengths.

There are no inherent gaps or discrete jumps between different regions of the spectrum, as the frequency and wavelength can vary smoothly and gradually.

Particle-wave duality:

Electromagnetic radiation exhibits both particle-like (photons) and wave-like properties.

This particle-wave duality allows for a continuous spectrum, as the properties of electromagnetic radiation can smoothly transition between these two perspectives.

Atomic and molecular transitions:

The emission and absorption of electromagnetic radiation by atoms and molecules occur through continuous transitions between energy levels.

These transitions can take place across a wide range of frequencies, contributing to the continuity of the spectrum.

Blackbody radiation:

The electromagnetic radiation emitted by a perfect blackbody, such as the Sun, is continuous and covers a wide range of frequencies.

This blackbody radiation is a fundamental source of the continuous electromagnetic spectrum.

In summary, the unified nature of electromagnetic theory, the continuous range of frequencies and wavelengths, the particle-wave duality, and the underlying atomic and molecular processes all contribute to the continuous nature of the electromagnetic spectrum.

Types of electromagnetic radiation:

Let us discuss each region of the electromagnetic spectrum in detail.

1. Radio waves:

Radio waves are the lowest frequency radiations in the entire electromagnetic spectrum. Conversely, they have the highest wavelengths.

Their frequencies lie below 10¹⁰ Hz. And wavelength lies below 10^-3 m

Heinrich Hertz discovered radio waves in 1886. Alternating currents of broadcast antennas produce them.

The communication systems such as radio and television broadcasting, cellular telephones, Wi-Fi networking, GPS (Global positioning systems), and navigation beacons utilize radio waves. Besides, submarine communications use low-frequency radio waves.

Modulating the amplitude of radio waves conveys only sound in AM radio transmission. But frequency modulation transfers sound and images to radios or televisions in FM radio transmission. To carry more data per unit of time, the frequency of radio waves used in FM transmission should be higher.

2. Microwaves:         

The German physicist Heinrich Hertz discovered microwave radiation. Their frequency varies between 10⁹ -10¹² Hz and their wavelength range from 1 meter to 1 millimetre.

Alternating currents of electric circuits and devices, cosmic radiations, and vacuum tubes such as Klystron, Magnetron, and IMPATT diodes are the sources that produce microwaves.

Wi-Fi routers, wireless devices such as Bluetooth, headphones, audio earpieces, and cell phones modulate assigned microwave frequencies for communications. Not only this, radar and other satellite communication systems also utilize microwaves. Furthermore, it is helpful in medical diathermy and industrial heating.

Atmospheric gases absorb microwave radiations of frequencies 100GHz to 30THz. Consequently, digital data such as audio, video files, and cellular communications do not employ microwave radiations of these frequencies.

The usual beneficiation of microwave radiation is to cook food in ovens. Their phenomenon of releasing energy by penetrating the inner layers of a substance operates microwave ovens.

Microwave ovens heat the food items containing water molecules. When the frequencies of microwave radiation and water molecule are the same, the oscillating electric field of radiation exert torque on water molecules. Polar water molecules bind together due to dipole moment by the exerted torque. Then radiant energy is supplied to food by the thermal motion of bonded water molecules. It heats the food.

3. Infrared region:

William Herschel discovered infrared radiation in 1800. Its frequency ranges from 300 GHz to 400 THz. And its wavelength varies from 1 mm-750 nm.

Infrared radiations are invisible, but we sense their heat. Hence they are known as heat radiations.

Thermal, vibration, rotational motions and electron transitions at the atomic and molecular levels produce infrared radiation.

Sunlight is a vital source of infrared radiation on the earth. Greenhouse gases trap and radiate these heat radiations to maintain the average earth surface temperature.

Heat sensors, thermal imaging, night vision equipment, fiber optic cables, and electronic equipment remotes utilize infrared radiation. And they are helpful in physical therapy treatments.

The infrared region comprises three zones. They are near-IR, middle-IR, and far-IR.

(i) Near infrared region:

It is IR-A zone whose wavelength ranges between 700-1400 nm. Being the lowest wavelength radiation, it transfers more heat energy to the surrounding.

It lies after the red light of visible radiation. Thus it exhibits some properties of visible light, such as reflection and polarization.

Some photographic films and image sensors detect these IR-A region radiations.

(ii) Middle infrared region:

It is called the IR-B region and has a wavelength range between 1400-3000 nm.

Predominant molecular vibrations of compounds absorb IR-B radiations. Consequently, it is a crucial zone for the absorption spectrum of chemical substances.

(iii) Far infrared region

It is known as the IR-C region. Its wavelength ranges from 3000 nm to 0.1 mm.

Rotational modes of gas molecules and molecular vibrations of liquids absorb radiations of this region.

Earth's atmosphere water molecules absorb these IR-C radiations to render an opaque effect. Within this opaque range, the radiations below 200μm wavelength allow partial transmission, which plays a vital role in astronomical studies.

4. Visible region:

We call it light. Sun is the only contributor of visible light on earth mainly. Vibrational, rotational, and electron transitions at atomic and molecular levels emit visible light.

The wavelength of visible light varies from 400 nm to 750 nm. Its frequency ranges from 7.5 X 10¹⁴ Hz to 4 X 10¹⁴ Hz.

 We could see the light but were unaware of its color composition (VIBGYOR) until Isaac Newton discovered the spectrum.

The seven colors of visible light are violet, indigo, blue, green, yellow, orange, and red. Among them, violet light is higher frequency radiation, and red light is the lowest frequency radiation.

It is a vital constituent of plants' photosynthesis, with which entire living bodies of the earth gets food.

5. Ultraviolet radiation:

Johann Ritter discovered UV radiation in 1801. It lies between visible and x-ray zones of the electromagnetic spectrum with a wavelength from 400 nm to 10nm and a frequency from 10¹⁵ Hz to 10¹⁷ Hz.

It is ionizing radiation that ejects electrons from the atoms.

UV light causes fluorescence in many substances.

It produces vitamin D in the human body and sterilizes medical equipment. It is also used in water purifiers to kill germs.

It consists of three regions. They are UA-A, UV-B, and UV-C.

(a) UV-A

Its wavelength ranges from 320-400 nm.

It lies close to the visible light of the electromagnetic spectrum.

It has the lowest frequency. Hence, the lowest energy.

Ozone is transparent to UV-A light. Moreover, 99% of ultraviolet radiation reaching the earth is UV-A.

(b) UV-B

Its wavelength lies between 290-320 nm.

Ozone absorbs it. So, little amount of UV-B light reaches the earth’s surface.

It has more energy than UV-A. Exposure to UV-B light leads to skin diseases and skin burns. Excess exposure can cause severe skin damage.

(c) UV-C

It has shortest wavelength of 220-290 nm and high energies comparable to that of X-rays.

Hence, it damages our skin cells heavily, leading to several skin disorders like cancer compared with UV-A & UV-B.

Glass absorbs UV light. Therefore, sitting behind glass doors or windows help to avoid skin damages.

But thanks to god for creating ozone to filter these harmful UV-C radiations reaching earth.

6. X-rays:

Wilhelm Rontgen's boon to medical science was the invention of X-rays in 1895. X-rays are used in medical imaging as they pass through many substances with little absorption. Also, their high penetrating power helps to treat cancer cells.

Their wavelength ranges from 10^-9 m to 10^-12 m, and their frequency lies between 10¹⁷ Hz to 10²⁰ Hz.

Stellar corona, neutron stars, and black holes emit X-rays. So, X-rays are significant in astronomical studies.

Additionally, they play a crucial role in spectral studies as electron transitions involving the innermost orbitals of an atom generate X-rays.

X-rays interact with matter by the Compton effect due to their high energies. The two types of X-rays are soft and hard X-rays.

(i) Hard X-rays:

Their wavelength lies between 0.2-0.1 nm.

Due to high energy, they have more penetrating power than soft X-rays. And are helpful in medical radiography and airport security.

They are also used in X-ray crystallography techniques to investigate crystal structures.

(ii) Soft X-rays:

Their wavelength lies above 0.4 nm

They have less energy. Hence, less penetrating power.

7. Gamma rays

Paul Villard discovered the shortest wavelength radiations of the electromagnetic spectrum in 1900. They have the highest frequencies and energies.

A gamma ray wavelength lies below 10^-12 m. And its frequency varies between 10²⁰ Hz to 10²⁵ Hz.

The nuclear decay of radioactive substances gives gamma rays.

Their high penetrating power is essential for the diagnostic imaging of nuclear medicine.

Cancer therapy employs gamma rays to destroy living cells. Also beneficial in the sterilization of seeds and irradiation of food materials.

Analysis of high-energy objects and regions of the universe utilizes energetic gamma photons.

Difference between electromagnetic wave and a matter wave

Electromagnetic wave	Matter wave
It associates with mutually perpendicular electric and magnetic fields.	Matter waves associate with material particles.
Electromagnetic waves do not require any medium for their propagation as they can propagate through space.	Matter waves require a medium such as solid, liquid, or gas for transmission. It can not pass through space.
All electromagnetic waves possess an equal velocity of 3x108 m/sec in a vacuum.	Different matter waves possess varying velocities depending on the nature of the transmitting medium. And it is always less than that 3x108 m/sec.
Sources such as the sun or celestial matter emit electromagnetic waves.	These are not emitted from the source as they associate with particles.
Electromagnetic waves have larger wavelengths. And it is calculated by the following formula. λ = c⁄ν	Matter waves have shorter wavelengths. The de-Broglie equation calculates the wavelength of matter waves. λ = h⁄mν

Multiple choice questions and answers on types of electromagnetic radiation

1. Which part of the electromagnetic spectrum has the highest frequency?

1. Radio waves
2. Microwaves
3. Gamma rays
4. X-rays

Answer:
Gamma rays
Explanation:
Gamma rays originate from highly energetic sources such as radioactive substances. Radiant energy varies directly with its frequency and inversely with its wavelength. The high energy-carrying gamma rays have the highest frequency and shortest wavelength than others in the electromagnetic spectrum.

2. Arrange the following electromagnetic radiations in the increasing order of their frequency

1. Radiations emitted from medical diagnosis
2. Traffic light signals
3. Emissions of microwave oven
4. FM radio tuning
5. Cosmic rays

Answer:
FM radio - Microwave - traffic light signals - medical diagnosis - cosmic rays
Explanation:
We use X-rays in medical diagnosis Traffic signals emit colored light radiations known as visible light A microwave oven uses microwave radiation to heat food items. FM radio processes the received radio waves to produce the sound. Cosmic rays are light radiations emitted from stars, galaxies, and other astronomical bodies in outer space. Their frequencies lie above 10²⁵ Hz to infinity.So, the increasing order of frequencies of the electromagnetic spectrum is ( Radio waves - Micro wave - visible light - X-rays - Cosmic rays)

3. Television broadcasts produce pictures by modulating

1. Amplitude
2. Wavelength
3. Phase
4. Frequency

Answer:
Frequency
Explanation:
We can transmit information by modulating a radio wave's frequency, amplitude, or phase. The AM radio transmission conveys only sound by modulating the amplitude of radio waves. Similarly, FM radio transmission carries sound and image data files by modulating the frequency of permitted radio waves.

4. Which of the following statement is true?

1. Both radio and sound waves are electromagnetic
2. Both radio and sound waves are mechanical
3. Both radio and sound waves transfer energy
4. Both radio and sound waves travel at the speed of light in a vacuum

Answer:
Both radio and sound waves transfer energy
Explanation:
The radio wave is electromagnetic. It does not require any medium for its propagation. Sound is a mechanical wave. It requires a medium for its propagation. Both radio and sound waves transfer energy to the surrounding. The velocity of radio waves in a vacuum is 3 x 10⁸ m/sec. And sound cannot travel in a vacuum. Its velocity in air is 333 m/sec.

5. Which of the following radiation is mainly absorbed by the atmosphere?

1. Infrared radiations
2. Near-ultraviolet radiations
3. Visible light
4. Far ultraviolet radiation

Answer:
Far ultraviolet radiation
Explanation:
Far ultraviolet radiation (UV-C) is the short wavelength radiation of 220-290 nm with high energy that can damage living cells. Ozone filters this highly energetic UV light of sunlight reaching the earth's surface, thus protecting living organisms.

6. Which part of the electromagnetic spectrum has the highest wavelength?

1. Radio waves
2. Microwaves
3. Gamma rays
4. X-rays

Answer:
Radio waves
Explanation:
Radio waves are the least energetic radiations in the electromagnetic spectrum. The photon energies vary inversely with the wavelength. Consequently, radio waves have the highest wavelength. At the same time, they have low frequency compared with the other six kinds of electromagnetic radiation.

7. Which of the following is not an electromagnetic wave property?

1. Photon
2. Heat energy
3. Angular momentum
4. Pressure

Answer:
Heat energy
Explanation:
Electromagnetic radiation is the flow of photons by modern quantum theory. Radiant energy flows in the direction of the propagation of the wave. Electromagnetic radiations do not transfer heat. Instead, it heats molecules and atoms by pumping radiant energy. The electromagnetic waves impart angular momentum in the interacting material. Electromagnetic waves exert pressure.

8. Which of the following is electromagnetic light?

1. Alpha rays
2. Beta rays
3. Gamma rays
4. Photons

Answer:
Gamma rays
Explanation:
Alpha rays are positively charged particles. Beta rays are negatively charged particles. Gamma rays are neutral and electromagnetic. Photons are packets of light energy.

9. Which of the following electromagnetic radiation has the same wavelength as the size of the nucleus of an atom?

1. Visible light
2. Infrared rays
3. Gamma rays
4. X-rays

Answer:
Gamma rays
Explanation:
The size of the nucleus of an atom is 10^-12 to 10^-13 cm. The wavelength of gamma rays ranges nearly from 10^-14 to 10^-16 cm.

10. For radar communications, we employ which of the following electromagnetic radiation?

1. Radio waves
2. Microwaves
3. Gamma rays
4. X-rays

Answer:
Microwaves
Explanation:
Microwaves of assigned frequencies were found helpful for radar and satellite communications.

11. Which of the following visible light has the shortest wavelength?

1. Red
2. Violet
3. Green
4. Blue

Answer:
Violet
Explanation:
The seven colors of visible light are violet, indigo, blue, green, yellow, orange, and red. Among them, violet light is higher frequency radiation. And it has the shortest wavelength.

12. Which of the following is the use of ultraviolet light?

1. Radar communications
2. Sub-marine communications
3. Radio and television communications
4. Sterilizing surgical instruments

Answer:
Sterilizing surgical instruments
Explanation:
UV light is energetic ionizing radiation that kills germs. Hence, we utilize it in the sterilization of surgical instruments.

13. Which radiation has more penetrating power in the electromagnetic spectrum?

1. Microwaves
2. Gamma rays
3. X-rays
4. Radio waves

Answer:
Gamma rays
Explanation:
Gamma rays are the most energetic radiations of the electromagnetic spectrum. Hence, they have more penetrating power than the others.

14. Which among the following are the heat radiations of the electromagnetic spectrum?

1. Microwaves
2. Infrared rays
3. Ultraviolet radiations
4. Gamma rays

Answer:
Infrared rays
Explanation:
Infrared radiations are invisible to the human eye. But we can feel the sensation of heat. Hence, it is also known as heat radiation.

15. Which of the following electromagnetic radiation investigates solid structures?

1. Microwaves
2. Gamma rays
3. X-rays
4. Radio waves

Answer:
X-rays
Explanation:
Hard X-rays being energetic, have a high penetrating power. Hence, they are used in X-ray crystallography to study solid structures.

16. Which of the following radiation cures muscle aches?

1. Infrared rays
2. Gamma rays
3. X-rays
4. Visible light

Answer:
Infrared rays
Explanation:
The human body radiates strongly in the mid-infrared region of the electromagnetic spectrum. Hence, infrared radiations are helpful in physical therapy treatments.

17. The ultra-frequency band of radio waves is used in

1. Medical diagnosis
2. Satellite communications
3. Television and radio
4. Cellular phone communications

Answer:
Cellular phone communications
Explanation:
Transmission of all sorts of digital data, such as cell phone conversations, video images, or audio files, involves the conversion of a radio signal into binary digits at each frequency range. It enables clear data transmission even with weak network signals. The higher the frequency of radio waves used in FM transmission, carries more data per unit of time.

18. The waves used in artificial satellites to provide communications are

1. Microwaves
2. Gamma rays
3. Infrared rays
4. Radio waves

Answer:
Microwaves
Explanation:
Microwave radiations have long wavelengths and can travel through large distances in the earth's atmosphere. Hence, they are helpful in artificial satellite communications.

19. Which of the following radiations are helpful in cancer treatments?

1. Ultraviolet radiations
2. Gamma rays
3. Infrared rays
4. Radio waves

Answer:
Gamma rays
Explanation:
Gamma rays are the most energetic radiations of the electromagnetic spectrum. Hence, they transfer more energy to living cells and damage them heavily. So, gamma rays are effective in killing cancer cells in the human body.

20. Which of the following radiations are not suitable for remote sensing?

1. Microwaves
2. Gamma rays
3. X-rays
4. Infrared radiation

Answer:
X-rays
Explanation:
Earth’s atmosphere absorbs the shortest wavelength radiations, such as gamma rays, X-rays, and ultraviolet rays. The inner layers of the atmosphere are opaque to X-rays. As a result, it disables the sensors of satellites. Hence, X-rays cannot fit for remote sensing.

21. The wavelength of X-rays is of the order of

1. One centimeter
2. One millimeter
3. One Angstrom
4. One kilometer

Answer:
One Angstrom
Explanation:
X-rays wavelength lies between 10^-8 m to 10^-12 m.

22. Which of the following condition to be maintained in a microwave oven to heat a food item containing water molecules?

1. Infrared radiations produced in the microwave oven heat the food item.
2. More water molecules in food items help to speed up the cooking.
3. The frequency of microwave radiations must be the same as that of the resonance frequency of water molecules
4. The temperature of the microwave oven should be above absolute zero

Answer:
The frequency of microwave radiations must be the same as that of the resonance frequency of water molecules
Explanation:
Micro wave expels energy by penetrating the material. Microwave ovens operate on this phenomenon of microwave radiation. Microwave ovens heat the food items containing water molecules when the frequency of radiation is the same as that of resonance frequencies of water molecules in the food item. The oscillating electric field of microwave radiations exerts a torque on water molecules. Due to the dipole moment, the water molecules attach among themselves by the exerted torque. By the thermal motion of water molecules, microwave energy circulates to heat the food.

23. Which of the following radiation is most dangerous to humans?

1. Ultraviolet radiation
2. Gamma rays
3. X-rays
4. Infrared radiation

Answer:
Ultraviolet radiation
Explanation:
Due to short wavelengths and more energies, ultraviolet radiation damages human skin cells giving severe skin diseases. Excess exposure to ultraviolet radiation causes skin cancer.

24. Which of the following radiation is absorbed by the glass?

1. Ultraviolet radiation
2. Gamma rays
3. Visible light
4. Infrared radiation

Answer:
Ultraviolet radiation
Explanation:
The glass absorbs UV light. Therefore, sitting behind glass doors or windows helps to avoid skin tanning.

25. Which of the following is ionizing radiation?

1. Ultraviolet radiation
2. Gamma ray
3. Visible light
4. Infrared radiation

Answer:
Gamma ray
Explanation:
The electromagnetic radiations having frequencies from 10⁹ to 10¹⁴ Hz are non-ionizing. Similarly, electromagnetic waves having more than 10¹⁶ Hz frequency are ionizing.